A need has existed for an effective device by which a number of members, such as grapple hook tines, can be selectively locked in prescribed angular relationships about a central axis. A need has also existed in such devices for the capability of unlocking the individual members and pivoting them to a different angular relationship. In grapple hooks, for example, the need is to selectively, yet securely lock the grapple hook tines in operative, substantially radial orientations for use; then to facilitate unlocking of the hook tines for pivotal folding movement to closed, storage conditions. Similar needs exist in other apparatus where it is desirable to securely lock expandable frames in their outwardly expanded condition. The above needs are recognized, to a limited degree, in the following United States patents.
U.S. Pat. No. 4,145,835 to Snow discloses a spring operated folding grapple. The device disclosed includes a pair of pivoted members and an integral camming mechanism that imparts pivotal motion of the two members responsive to axial motion of one member between a flat storage condition and a expanded condition wherein the hook flukes are oriented perpendicular to one another. Movement of one of the members is dependent upon corresponding movement of the other. A locking pin is provided to hold the flukes in the expanded condition.
A somewhat similar structure is shown in U.S. Pat. No. 4,130,961 also to Snow. In this device, flukes of the grapple hooks are welded together and arranged in such a manner that an axial pulling force on one hook pair will result in pivotal motion of that pair to an expanded, operable condition in relation to the remaining pair.
U.S. Pat. No. 2,602,869 to Matz discloses a collapsible hook structure having a sliding plate used for both expanding the several pivoted hooks of the device and for holding the hooks against individual pivotal movement while at the expanded position.
U.S. Pat. No. 3,092,412 to Drake discloses a grab hook having foldable hook tines. The tines are foldable from a relatively flat configuration overlying one another to an operative condition wherein the tines are substantially radial about a central axis. A threaded wedge nut is utilized to axially clamp against the hook flukes. Grooves within the wedge member receive portions of the flukes to hold them in the radial positions by a axial clamping action between the grooves and an outside sleeve.
U.S. Pat. No. 1,031,903 to Anderson discloses a gaf hook that includes foldable hook members. The individual hook members fold about axes that are situated in a plane substantially perpendicular to the central support for the hooks. The hooks fold individually through arcs of approximately 180.degree. to an operative position wherein the pointed hook ends face outwardly. They also fold to an inoperative position in which the pointed hook ends face inwardly and the hook shanks extend in a direction opposite the direction of extension. A sliding collar is provided on the support to releasably hold the hooks in either operative or inoperative positions.
Of the above references, none disclose the positive locking arrangement as disclosed herein by which individual pivoted members may be quickly yet securely held in an operative position by means of mechanism that is relatively simple yet reliable and extremely easy to operate. This is a definite need, especially in areas where the associated device (such as a grapple hook) is to be used in a critical situation as, for example, when the apparatus is used as a grapple hook in climbing or descending.